The present invention relates to door latch mechanisms for holding doors in a closed position. More particularly, the present invention relates to rod linked, door latch mechanisms for fire doors.
Commercial or public buildings are typically required to provide for emergency exit in the event of a fire. One common variety of emergency exit is a latch closed double door, about eight feet high and equipped on its inside with panic bars or push pads. Pushing the panic bar or push pad toward the door releases two or more door latches, permitting opening of the door and escape of the building occupant.
For example, U.S. Pat. No. 4,974,890 to Cohrs, assigned to Von Duprin, Inc., the disclosure of which is hereby incorporated by reference, discloses a vertical rod exit device for a double door. Top and bottom latch mechanisms are connected by vertically extending rods to a push pad. Pushing the push pad toward the door causes retraction of the rods away from the latch mechanisms, and consequent release of latches holding the door in a closed position against a door frame.
However, the latch mechanism described in U.S. Pat. No. 4,974,890 may not provide a suitable latching action during sustained fires, especially if the door is over eight feet in height. Buckling and folding of the rods as a result of the intense heat of a fire can cause release of the latches holding the door closed. To overcome this problem, a mechanism for preventing disengagement of the latches due to fire is needed.
The foregoing illustrates limitations known to exist in present devices and methods. Thus, it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, a suitable alternative is provided including features more fully disclosed hereinafter.